The present invention relates to spools for film or other web material wherein the spool has a slot with a hook in the slot for engaging the film through apertures in an end portion of the film.
Spools for film and other webs may have a slot through the core of the film with hooks in the slot for engagement with the film through apertures in the film. Such spools are known, for example, from copending U.S. patent application Ser. No. 237,027, filed Aug. 29, 1988 in the names of Clark E. Harris et al and entitled "Spool for Web-Shaped Film", now U.S. Pat. No. 4,852,821. A spool as disclosed in such application is generally designated 10 in FIGS. 1 and 2 and comprise a generally cylindrical core 12 on which film is wound and a pair of annular flanges 14 at the end portions of the core. A slot 16 extends through the core 12 of the spool and has an entrance end 17 and an exit end 19. Two hooks 18 project into the slot from a wall 20 at one side of the slot. A rib 22 on a second wall 24 projects into the slot between the hooks 18 and serves to deflect the film downwardly over the hooks as it is initially fed through the slot 16 from the right toward the left as viewed in FIG. 2. Wall 20 of the spool has a narrow notch 26 immediately below rib 22. As shown in FIG. 1, the notch does not extend axially into the area of wall 20 beneath the tip ends of the hooks or between the hooks and the exit end of the slot.
Spools of this kind are manufactured on molding machines and placed in containers in bulk form for transport to spooling apparatus. In the spooling equipment the spools may be placed in a vibrating hopper, for example, which automatically separates individual spools from the other spools and feeds them sequentially to a winding station of the spooling apparatus.
During the bulk handling of the spools as described above, it is possible for a flange 14 of one spool to become locked in the exit end 19 of the slot of another spool, as illustrated in FIGS. 1 and 2. This can occur because the thickness of flanges 14 of the spools is approximately equal to or a little smaller than the spacing between the bottom of rib 22 and the top of wall 20. Also, as best shown in FIG. 1, the arcuate portion of the flange 14 that can enter the exit end of the slot is wider than the notch 26. If two spools become locked together, the spools cannot be separated and fed sequentially to the winding station of the spooling apparatus as described above. As is apparent from FIG. 2, a flange 14 can penetrate the exit end of the slot 16 only to a limited extent, i.e., until the flange reaches the adjacent tip ends of the hooks 18, because the tip ends of the hooks are spaced from wall 20 by a distance less than the thickness of the flanges 14.
This locking problem could be avoided by increasing the thickness of flange 14 or rib 22. However, hundreds of millions of spools of this type may be made each year by large film manufacturers, and the additional cost of even an incremental increase in material used for forming the spools can significantly increase the cost of producing the spools. Moreover, an increase in the width of flange 14 can result in deviations from standard specifications and may adversely effect performance of the spools in cassettes formed around the spools or in film processing equipment. Accordingly, it is desirable to solve the locking problem without increasing the cost of the spools, and it is even more desirable if the problem can be solved by further reducing the amount of material used in the spool to thereby further reduce its cost.